docs(matrix): Antigravity runs hook commands through cmd.exe on Windows (AGY-3a)

[jothimani-rajendran]

What this changes

Antigravity's matrix.json notes now carry what the owner's witness run on 2026-10-18 found (Antigravity IDE, Windows 11, version not recorded; source: org-plan witness/results/witness-antigravity-2026-10-18.md at 16ca2e2):

• The corrected hooks.json loaded. Antigravity named the hook jsonhook__agentseam_PreToolUse_0_0 and ran it.
• On Windows a hook command runs through cmd.exe. A single-quoted argument split inside git (unknown option: -f), and cmd.exe ran the rest ('{' is not recognized ...). With \" quoting, git still failed (unknown option: -f, exit 129).
• A command with no quotes and no space inside any argument worked: the guard was refused, the turn-end gate was refused, and a benign git status ran.
• A hook that exited 1 halted the tool call.

The note says plainly that the cmd.exe and \"-escaping mechanism is inferred from the error text. It was not read from vendor docs or source. The old sentence "The corrected file has not been run." now says the file loaded in this run.

Why notes, not a schema field: I followed the goose sh -c precedent (#213). That fact went into the matrix row's notes, and nothing in the vendor schema reads a spawn-shell fact today. AGENTS.md says the matrix is data and claims never exceed it. A new field with no reader would be data that no code checks. The consumer change (chock AGY-3b, a quote-free command for Antigravity on Windows) can add a field if it needs one.

Claim check

• No capability claim is widened. No claim, adapter, schema or vendor JSON changed. fail_mode stays open, even though one run saw exit 1 halt a call. Nothing is marked witnessed.
• No MATRIX row added or re-dated
• Primary source: the owner's witness run, cited above

Checks

• pytest -q: 2626 passed, 6 skipped
• ruff check . and ruff format --check . pass
• examples/generate.py --check: up to date (18 files). Only examples/generated/antigravity.md changed.
• Stdlib-only: no code changed
• Signed off

Notes for the reviewer

Only the antigravity row changed. Two files: src/agentseam/data/matrix.json and examples/generated/antigravity.md.

Generated by Claude Code

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Generated by Claude Code